In known types of nuclear power reactors, for example as used in the Dresden Nuclear Power Station near Chicago, Illinois, the reactor core comprises a plurality of spaced fuel assemblies arranged in an array capable of self-sustained nuclear fission reaction. The core is contained in a pressure vessel wherein it is submerged in a working fluid, such as light water, which serves both as coolant and as a neutron moderator. Each fuel assembly comprises a removable tubular flow channel, typically of approximately square cross section, and formed for example of zirconium alloy, surrounding an array of elongated, cladded fuel elements or rods containing suitable fuel material, such as uranium or plutonium oxide, supported between upper and lower tie plates. A typical fuel assembly of this type is shown, for example, by B. A. Smith et al. in U.S. Pat. No. 3,431,170.
Additional information on nuclear power reactors may be found, for example, in "Nuclear Power Engineering", M. M. El-Wakil, McGraw-Hill Book Company, Inc., 1962.
The previously mentioned removable tubular flow channel which surrounds each fuel assembly is an example of a reactor component which potentially has a relatively long service life. Thus upon verification of its serviceability it can be reused on a replacement fuel assembly.
Apparatus which can be used at the reactor site for examining irradiated components such as flow channels to verify continued serviceability has been developed. For example, U.S. Pat. No. 4,143,251 describes a device for measuring the corrosion formation on the surface of such components while U.S. Pat. No. 4,197,652 describes a device for checking the dimensions of such components.
If such a component is found to be unserviceable, it is discarded. However, because it is radioactive, it cannot be scrapped in a conventional manner. The usual procedure is to place the rejected component in an underwater storage rack to await processing (such as compaction) for eventual permanent disposal.
With a view toward understanding the nature and causes of defects of such rejected components, so that improvements can be made, or for detailed examination of experimental or developmental components, it is found desirable to examine the portions of such components with laboratory equipment and techniques beyond those available as a practical matter at a reactor site.
The desire for laboratory examination of the defective portions raises several problems. Since only selected samples of the rejected component are needed for laboratory examination, transportation of the entire component is impractical and would merely transfer the problem of storage of the component from the reactor site to the laboratory. Thus the desired sample pieces should be cut from the component, such as a flow channel, at the reactor site and only these sample pieces transported to the laboratory.
Furthermore, while the reactor site is equipped to handle and store flow channels (and other components) as such, usually it is not well equipped to accommodate odd sized and shaped pieces that would result, for example, from cutting a fuel channel in two. Thus it is desirable to remove sample pieces from the rejected component without destruction of its structural integrity or change in its overall size and shape.
An object of this invention is remotely operable apparatus for removing sample pieces from an irradiated component.
A more specific object is apparatus which is remotely manipulatable for making cuts in the walls of an irradiated component whereby sample pieces can be removed without destroying the structural integrity of the component or changing its overall size and shape.